Medical professionals and cytotechnologists frequently review biological specimens affixed to a specimen carrier, such as a slide, to analyze whether a person from whom the specimen was obtained has or may have a particular medical condition. For example, it is well known to examine a cytological specimen in order to detect the presence of malignant or pre-malignant cells as part of a Papanicolaou (Pap) smear test. To facilitate this review process, automated systems have been employed to perform a pre-screening of the specimen slides in order to focus the cytotechnologist's attention on the most (or at least more) pertinent cells or groups of cells in the respective specimen, while discarding less relevant cells from further review. One such automated imaging system is the Thinprep Imaging System, available from Cytyc Corporation, 250 Campus Drive, Marlborough, Mass. 01752 (www.cytyc.com).
FIG. 1 generally illustrates a known imaging system 10 that includes a processor, computer or controller 11, an optical stack 12 and a robot for feeding and removing specimen slides 14 to and from the optical stack 12. An optical stack 12 includes a motion control board computer or controller 20, a stage 21, a light source 22, a lens 23 and a camera 24. Images generated by the optical stack 12 are provided to the computer 11 for analysis. The robot 13 takes a slide 14 from a cassette 30 and places the slide 14 on the stage 21. The computer 11 controls the MCB computer 20 so that the MCB computer 20 moves the stage 21 to location the slide 14 under the camera 24 and the lens 23. The light source 22 is activated, and an image of a portion of the specimen on the slide 14 is acquired by the camera 24 and provided to the computer 11. The computer 11 instructs the MCB computer 20 to move the stage 21 and the slide 14 thereon a very short distance from a first location to a second location. An image of the next portion of the specimen on the slide 14 at the second location is acquired by the camera 24 and provided to the computer 11.
The stage 21 is moved to a different location after an image is taken of different portions of the specimen on the slide 14. A first portion of the specimen is imaged when the stage 21 is at a first stage location. The stage 21 is moved to a second location, and an image of a second portion of the specimen is acquired at the second location. The stage 21 is moved to a third location, and an image of the third portion of the specimen is acquired, and so on for each portion of the specimen until the entire specimen is imaged. In known imaging systems, the stage 21 can be moved about 2,400 times to acquire 2,400 images of 2,400 different portions of a specimen. The robot 13 then removes the imaged slide 14 from the stage 21 and places another slide 14 from the cassette 30 onto the stage 21 for imaging as described above.
After images of the specimen are acquired, the images are processed to identify or rank cells and cell clusters that are of diagnostic interest. In some systems, this includes identifying those cells that most likely have attributes consistent with malignant or pre-malignant cells and their locations (x-y coordinates) on the slide. For example, the processor 11 may select about 20 fields of view, e.g., 22 fields of view, which include x-y coordinates identifying the locations of cells and cell clusters that were selected by the processor 11. This field of view or coordinate information is provided to the microscope (not shown in FIG. 1), which steps through the identified x-y coordinates, placing the cells or clusters of cells within the field of view of the technician. While current imaging systems and methods for selecting portions of images for further review have been used effectively in the past, they can be improved.
For example, referring to FIG. 2, if the cells are consistent with pre-malignant cells or malignant or cancerous cells 42 (generally identified by “C”), then the selected fields of view 40 ideally identify these cells or regions so that the cytotechnologist is directed to those cells or clusters during review. Although FIG. 2 illustrates each field of view 40 having cancerous cells, it should be understood that some fields of view have regular cells, whereas other fields of view have non-cancerous cells, but the processor 11 is configured to identify cells or regions 42 that are most consistent with pre-malignant and malignant or cancerous cells.
Referring to FIG. 3, in some cases, however, there may be normal, non-cancerous cells, e.g., repair cells 44 (identified by “R”), which are normally dividing cells that are generated to replace or repair damaged tissue. These repair cells 44 may appear similar to pre-malignant or malignant cells 42 that would otherwise be selected by the processor 11 since repair cells 44 and cancerous cells 42 both include dividing nucleus components. Consequently, normal repair cells 44 may result in “false alarms” in that they may be ranked higher than other malignant or pre-malignant cells 42 that would otherwise be selected by a processor 11 if the false alarm cells were not selected. Thus, when repair cells 44 are analyzed, the processor 11 may select fields of view that include higher ranking non-cancerous cells instead of other fields of view that include more relevant cells (possibly cancerous cells). The fields of view that should have been selected are generally illustrated by dotted lines in FIG. 3. Thus, the cytotechnologist may not be presented with the most relevant fields of view, possibly resulting in a less accurate diagnosis.